The present invention relates to a continuous press forming method of a sheet resin, which method is comprises the steps of extruding a molten resin, forming the molten resin into a sheet resin strip, cutting the sheet resin strip into sheet resin pieces and press forming the sheet resin pieces on a consecutive basis.
The press forming of sheet resins is generally referred to as stamping molding or compression molding and adopted to mold a drawn formed product of a relatively large size, which is not suitable for being subjected to injection molding and also in molding a fiberglass-containing resin, which is difficult to be processed by injection-molding. This is because press molding makes it possible to effect release molding by use of a generally known press machine.
Generally, a merchant buys a semi-fabricated material manufactured in the form of a sheet resin by the manufacturer of raw material, and processes it into a sheet resin product in such a way that the resin material is softened with heat and the softened resin material is injected into a molding die by hand. This method of forming a sheet resin by use of a press has come to find increasingly popular acceptance. However, a typical machine used to practice such a method employs a very expensive sheet resin and utilizes much electric power to have the sheet resin softened. Also poor workability and producibility is involved in such a method. When the sheet resin, once hardened, is again softened with heat, resin specks inevitably occur inside and on the surface of the sheet resin. Even if a high temperature process for producing the sheet resin is carried out to prevent occurrence of such resin specks, there is a possibility of causing deterioration of the surface of the sheet resin, giving rise to chaps and cracks on the surface of the sheet resin product. This reduces the reliability of the sheet resin in respect to strength.